Complexation of Tetrakis(acetato)chloridodiruthenium with Naphthyridine‐2,7‐dicarboxylate – Characterization and Catalytic Activity

New insights into progressive ligand replacement from [Ru2Cl(O2CCH3)4]: synthetic strategies and variation in redox potentials and paramagnetic shifts

The complete series of [Ru₂Cl(Dp-FPhF)_x(O₂CCH₃)_4-x] (x = 1-4; Dp-FPhF^- = N,N'-bis(4-fluorophenyl)formamidinate) compounds, has been prepared and characterized by a multi-technique approach, including single crystal X-ray diffraction. A careful study of the different methodologies has allowed us to prepare four compounds with good yields and without an inert atmosphere or further purification. Specifically, [Ru₂Cl(Dp-FPhF)(O₂CCH₃)₃] (1) was obtained using an ultrasound-assisted (USS) method, while [Ru₂Cl(Dp-FPhF)₄] (4) was prepared by microwave assisted solvothermal synthesis (MWS). The intermediate substitution products cis-[Ru₂Cl(Dp-FPhF)₂(O₂CCH₃)₂] (2) and [Ru₂Cl(Dp-FPhF)₃(O₂CCH₃)] (3) have been prepared by conventional heating, controlling the molar ratio of the starting materials. ESI-MS and infrared spectroscopy were used to follow all the reactions and permitted a qualitative evaluation of the axial reactivity in this series. Magnetic and absorption measurements confirmed a high spin σ²π⁴δ²(π*δ*)³ electronic configuration in all cases. However, the effect of the gradual modification of the electronic density in the diruthenium core markedly affects other properties. The cyclic voltammograms of the compounds show a strong decrease in the one electron oxidation potential and an increase in the reduction potential in the series from 1 to 4. Furthermore, despite their paramagnetic nature, ¹H- and ¹⁹F-NMR spectra were recorded, and a correlation between the paramagnetic shift of the signals and the substitution degree of the diruthenium species was observed. These results provide a comprehensive guide to synthesise and understand the effects of equatorial ligand substitution on the properties of Ru₂⁵⁺ compounds.

Ultrasound-assisted synthesis of water-soluble monosubstituted diruthenium compounds

The elusive monosubstituted diruthenium complexes [Ru₂Cl(DAniF)(O₂CMe)₃] (1), [Ru₂Cl(DPhF)(O₂CMe)₃] (2), [Ru₂Cl(D-p-CNPhF)(O₂CMe)₃] (3), [Ru₂Cl(D-o-TolF)(O₂CMe)₃] (4), [Ru₂Cl(D-m-TolF)(O₂CMe)₃] (5), [Ru₂Cl(D-p-TolF)(O₂CMe)₃] (6) and [Ru₂Cl(p-TolA)(O₂CMe)₃] (7) have been synthesized using for the first time ultrasound-assisted synthesis to carry out a substitution reaction in metal-metal bonded dinuclear compounds (DAniF^- = N,N'-bis(4-anisyl)formamidinate; DPhF^- = N,N'-diphenylformamidinate; D-p-CNPhF^- = N,N'-bis(4-cyanophenyl)formamidinate; D-o/m/p-TolF^- = N,N'-bis(2/3/4-tolyl)formamidinate; p-TolA^- = N-4-tolylamidate). This is a simpler and greener method than the tedious procedures described in the literature, and it has permitted to obtain water-soluble complexes with good yields in a short period of time. A synthetic study has been implemented to find the best experimental conditions to prepare compounds 1-7. Two different types of ligands, formamidinate and amidate, have been used to check the generality of the method for the preparation of monosubstituted complexes. Five new compounds (2-6) have been obtained using a formamidinate ligand, the synthesis of the previously described compound 1 has been improved, and an unprecedented monoamidate complex has been achieved (7). The crystal structures of compounds 3 and 7 have been solved by single crystal X-ray diffraction. These compounds show the typical paddlewheel structure with three acetate ligands and one formamidinate (3) or amidate (7) bridging ligand at the equatorial positions. The axial positions are occupied by the chloride ligand giving rise to one-dimensional polymer structures that were previously unknown for monosubstituted compounds.

Synthesis and structural characterization of transition metal dithiolene derivatives containing divalent metals as counter-cations

Complexes containing [Fe₂(SC₆H₂Cl₂S)₄]²⁻ or [Ni(SC₆H₂Cl₂S)₂]⁻ entities and divalent metal cations as well as an 1D-coordination polymer K/Zn have been obtained and their magnetic behaviour studied.

Synthesis, structural characterization and catalysis of ruthenium(ii) complexes based on 2,5-bis(2'-pyridyl)pyrrole ligand

Treatment of the 2,5-bis(2'-pyridyl)pyrrolato (PDP^-) anion with {Ru(COD)Cl₂}_n in THF readily yielded [Ru(PDP)(COD)Cl] (1) in almost quantitative yield. Anion metathesis of 1 in organic solvent by NO₃^- and OTf^- (OTf^- = triflato) gave [Ru(PDP)(COD)(NO₃)] (2) and [Ru(PDP)(COD)(OTf)] (3), and in aqueous solution by BF₄^- and PF₆^- afforded aqueous complexes [Ru(PDP)(COD)(H₂O)](BF₄) (4+·BF₄^-) and [Ru(PDP)(COD)(H₂O)](PF₆) (4+·PF₆^-), respectively. Treatment of 1 with PhICl₂ in CH₂Cl₂ afforded 5 with halogenated pyrrole. These complexes exhibit similar structure, including one Ru(ii) atom, one 2,5-bis(2'-pyridyl)pyrrole and one monodentate anion or aqua ligand. Each Ru(ii) tightly binds to three adjacent coplanar sites of PDP^- ligand to form a meridional configuration. Complex 1 with NaIO₄ as the oxidant in EtOAc-CH₃CN-H₂O (ratio = 3 : 1 : 2) proved to be highly effective in the catalytic oxidation of olefins to carbonyl products.